Electrochemical advanced oxidation process (EAOP) as the novel treatment of chemical industrial wastewater is widespread concerned in China. PNP (P-nitrophenol) as the typical organic pollutant can be degraded totally in diluted effluents in previous studies, however, the process performed badly in the conditions with high salinity, and the toxic by-products formation aggravate pollution as well. In this paper, the transformation of electrolytes including Cl- and SO42- in EAOP have been studied, confirming the suitable concentration range for PNP degradation in a high level of salinity by considering the degradation rate of target organic and by-products formation. it was concluded that the suitable electrolytic concentration range is 500-5000 mM, and the organics treatment system should be set after nanofiltration section to make conditions with high salinity of NaCl. Finally, the breakup order of bond for PNP simulated in DFT method was hydroxyl group>nitro group>benzene ring, and the bond of benzene ring closest to hydroxyl group was prior attacked.